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(11) | EP 0 590 893 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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Knocking detection method for internal combustion engines and ignition timing control method Verfahren zur Klopferkennung bei inneren Verbrennungsmotoren und Zündungssteuerverfahren Méthode de détection de cliquetis dans des moteurs à combustion interne et procédé de contrôle d'allumage |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
1. Field of the Invention
[0001] The present invention relates to a detection method for detecting knocking in an internal combustion engine and an ignition timing control method.
2. Description of Prior Art
[0002] As is well known, knocking is a phenomenon resulting from a self-ignition of unburned gas remaining in the extremity region of the combustion chamber, and causing vibration in the gas inside the combustion chamber, consequently propagating thus generated vibration to the engine body itself.
[0003] Since this knocking gives rise to a loss of energy in the engine output, exerts mechanical shock on the components of the engine as well as lowers the fuel consumption and the like, it is desired to be avoided as much as possible. For this purpose, it is indispensable for a precise detection of the occurrence of a knocking to be ensured to be made.
[0004] Reflecting such requirements, there has been proposed a prior art as set forth in the Japanese Patent Laid-open No.58-45520/1983 wherein the occurrence of knocking is detected by going through the steps of separating resonance frequency components in the range of 5 to 20 kHz in the output signals from the vibration detection sensor with band pass filters, and determining whether a value is greater than the background level thereof.
[0005] However, such knocking detection method based on single resonance frequency components involves such problems that the background level thereof becomes larger at a faster engine speed and that the knocking resonance frequencies tend to change with varying engine data.
DESCRIPTION OF THE INVENTION
[0006] Therefore, in order to solve the problems associated with the prior art, there has been proposed a knock detection method as set forth in the Japanese Patent Laid-open No.3-47449/1991 (EP-A2,3-392 804) wherein the detection of knocking is carried out by sampling a plurality of resonance frequency components.
[0007] This knock detection method has been very innovative and successful in realizing a high precision knock detection, and thus has been highly appraised and accepted by the related industry.
[0008] Reflecting recent demands for further improvements in fuel consumption, exhaust emission cleaning capabilities and the like, many attempts to increase the compression ratio in the engine are under way. Increased compression ratios, however, in turn tend to cause a knocking readily to occur, thereby demanding further efforts to improve the knock detecting precision.
[0009] However, for an engine having a poor frequency characteristic, there exist such operational conditions and frequency bands which cause the background level thereof to temporarily or continuously change, for example, to decrease, depending on the performance of the vibration sensors employed, or positions of attachment thereof and the like.
[0010] Therefore, when there occurs that, for example, a background level utilized as a parameter for detecting the occurrence of knocking becomes abnormally small, there may be formed a false signal indicating an occurrence of knocking in at least one of the frequency bands of the plurality of resonance frequencies, notwithstanding that actually no knocking is caused therein.
[0011] Thereby, when there is formed a false signal indicating an occurrence of knocking at least in one of the frequency bands, nevertheless, in the plurality of resonance frequencies to be sampled for a precise detection of knocking, this false signal adversely affects the whole knocking determination performance over these resonance frequencies, consequently impeding further to improve the knocking detection precision.
[0012] According to a first aspect of this invention there is provided a knocking detection method as claimed in claim 1 herein.
[0013] According to a further aspect of this invention there is provided an ignition timing control method as claimed in claim 19 herein.
[0014] Since when any comparison component, i.e., background level varies abnormally a limit comparison component is adapted to be used instead of the abnormally varying comparison component, information on knocking is ensured to be obtained from the relationship between the limit comparison component and the characteristic component as well, thereby eliminating an issuance of abnormal information on knocking, thus improving the detecting precision of knocking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will be described more particularly in the following with reference to the accompanying drawings, in which;
Fig.1 is a flowchart illustrating a knocking detection method of one embodiment of the invention;
Fig.2 is a vibration waveform diagram without any knock generation;
Fig.3 is a vibration waveform diagram with a knock generation;
Fig.4 illustrates spectrum intensity of a knocking disclosed in EP-A-0 392 804;
Fig.5 illustrates another spectrum intensity of a knocking disclosed in EP-A-0 392 804;
Fig.6 illustrates power spectra with and without any knock generation;
Fig.7 is a vibration waveform diagram;
Fig.8 is a background level diagram;
Fig.9 shows a knock determination diagram;
Fig.10 shows lower limiter maps;
Fig.11 is a flowchart for reading out a lower limiter;
Fig.12 illustrates a calculation method for calculating a lower limiter;
Fig.13 is a flowchart illustrative of arithmetic operation of a lower limiter;
Fig.14 shows a system configuration of the invention;
Fig.15 shows a schematic block diagram of a control unit of the invention;
Fig.16 is a flowchart illustrating ignition calculation according to the invention;
Fig.17 shows a lower limiter map;
Fig.18 is a flowchart for reading out a lower limiter;
Fig.19 shows a lower limiter map;
Fig.20 is a flowchart for reading out a lower limiter;
Fig.21 shows a lower limiter map;
Fig.22 is a flowchart for reading out a lower limiter;
Fig.23 is a flowchart illustrating another embodiment of the invention;
Fig.24 is a diagram illustrative of switching between lower limiters;
Fig.25 is a chart diagram explaining acceleration steps;
Fig.26 is a flowchart illustrating still another embodiment of the invention; and
Fig.27 is a flowchart illustrating further embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0016] With reference to the accompanying drawings, one embodiment of the invention will be set forth in detail in the following.
[0017] At first, the knocking determination principle of the invention for determining an occurrence of a knocking will be explained. There are contained various vibration components in the vibration of an engine. Such vibration components include, for example, those caused by piston friction, crank shaft rotation, valve operation and the like. In addition, these vibrational components tend to vary responsive to engine conditions.
[0018] When knocking occurs in the engine, a characteristic vibration specific to knocking is generated. Thereby, determination of a knocking occurrence is realized by separating the characteristic vibration inherent to knocking from the whole vibration components of the engine detected by the vibration sensor.
[0019] Figure 2 shows a result of frequency analysis of an output frequency component from a vibration sensor when no knocking is present. On the other hand, Figure 3 shows a result of frequency analysis of an output frequency component from the vibration sensor when knocking is present.
[0020] As is obviously understood from the comparison of Figures 2 and 3, in the case where knocking is present, respective resonance frequency components tend to become larger than in the case where no knocking is present.
[0021] Next, with reference to Figures 4 and 5, a knocking occurrence determination method utilizing a knocking determination vector index will be described in the following. The operational principle of the invention will be described by way of example of resonance frequency components f10(6.3 kHz) and f01(13.0 kHz). They are, however, not limited thereto, and at least two of any resonance frequency components may be utilized for determining a knocking occurrence.
[0022] The vibration sensor detects a vibration which has been synthesized by combining a vibration component due to a knocking occurrence and one due to a background thereof. Thereby, when there is no knocking a knocking determination index I becomes an index Ib which is defined by the background vibration, while when there is knocking it becomes an index I which is defined so as to include the background vibration Ib and a vibration component Ik due to the occurrence of knocking.
[0023] The hereabove knocking determination index I can be formularized into the following equation including major resonance frequency components.
where, ω is a real value to be determined by an engine speed. Further, it may take a binary value of 1 or 0. P represents power spectra of respective resonance frequency components.
[0024] As shown in Fig.4, the knock determination vector index Ib which is expressed by the resonance frequency components of the background vibrations and the index Ik which is expressed by the resonance frequency components of the vibration resulting from the occurrence of a knocking have a different direction and magnitude from each other. This is because that, as in the audible test in which the occurrence of a knocking is identified by a crunching noise, there is involved a change in noise tone when a knocking occurs.
[0025] When the vibration component due to the occurrence of a knocking is added to the background vibration, the knock determination index I according to f01, f10 included in the original from the vibration sensor falls in a range below a knock determination threshold value I01 in Fig.4, and outside a dotted arch line of a threshold value I02 in Fig.5, thus enabling determination of the occurrence of knocking.
[0026] Further, in the present invention, any set of the plurality of resonance frequency components included in the output from the vibration sensor and utilized in combination, not limiting to the five elements on the right-hand term of Equation (1), is prescribed to be a knocking determination index.
[0027] When such a knocking determination index is utilized, the occurrence of any knocking is ensured to be determined even if a background vibration increases significantly since the composition of a characteristic frequency component indicative of a knocking relative to its corresponding background vibration is taken into consideration.
[0028] As set forth previously, there are some operational conditions and frequency bands where the background level decreases temporarily or continuously depending on the quality of the vibration sensors employed or their attachment positions, consequently causing a false signal indicative of the occurrence of a false knocking notwithstanding actually no knocking being present.
[0029] When attempting to obtain energy of the knocking resonance frequencies on the basis, for example, of a signal/noise (background) ratio, i.e., S/N ratio, an abnormal decrease in the background level in one of the resonance frequencies will cause its S/N ratio to become abnormally larger, which eventually affects the total determination processing thereof on the basis of the plural resonance frequencies, in effect curbing the efforts to improve the knocking detection precision.
[0030] In order to solve the hereinabove problems associated with the prior art, when a particular background level corresponding to at least one of the resonance frequencies decreases abnormally, the present invention is adapted not to utilize the abnormally decreased background level but to utilize a predetermined limit value, for example, background lower limiter.
[0031] In the following, a knocking detection method embodying the invention constituting a key portion thereof will be described in detail.
[0032] Figure 6 shows power spectra relative to the frequencies, in which the occurrence of a knocking is indicated by a curve represented by a solid line, while the non-occurrence thereof is represented by broken lines. It is clearly shown that power spectra of respective resonance frequency bands are increased due to the occurrence of knocking.
[0033] However, in case there exist characteristic frequencies inherent to a knocking having smaller power spectra as shown by f1 and f9, or in case there exist greater noise components depending on the nature of the engine as shown by A in Figure 7, there occurs such a phenomenon as shown by B in Figure 8 in which the background level is caused to drop abnormally.
[0034] Thereby, there has been a problem that an S/N ratio becomes abnormally large, eventually causing a final knocking determination index to be deviated, thereby giving rise to an erroneous judgment.
[0035] Thereby, it is arranged according to the invention to eliminate erroneous judgment on knocking by setting a lower limiter as shown by broken lines with respect to the background level in Figure 8.
[0036] First, with reference to Figure 1, the operation of a knocking occurrence determination process in a CPU according to the invention will be described in the following.
[0037] The flowchart in Figure 1 is executed for every detonation per cycle, and is activated by interrupting the CPU.
[0038] In step 101, an output signal from the vibration sensor is read after its analog to digital conversion in an A/D converter.
[0039] In the next step 102, a frequency analysis of the analog-to-digital converted signal from the vibration sensor is executed. This frequency analysis is carried out through a transform method such as the fast Fourier transform or Walsh transform.
[0040] Then, in step 103, a plurality of frequency bands each containing a resonance frequency are selected from the signals which have been subjected to the frequency analysis. In this embodiment of the invention, a total of eight resonance frequency bands are selected.
[0041] Upon selection of preferred frequencies at step 103, in the next step 104 an S/N ratio indicative of a power spectrum is obtained for each selected frequency.
[0042] Namely, there are obtained a plurality of selected frequencies (f1 ...... fi), i.e., f1 ...... f8 in this embodiment, and a plurality of corresponding background levels (BGL1 ...... BGLi), i.e., BGL1 ...... BGL8 in this embodiment, then an S/N ratio SLi=fi/BGLi is obtained for each frequency selected.
[0044] In the next step 105, a knock strength is obtained by sampling m numbers, in this embodiment 5, from the selected frequencies which are ordered in the decreasing order of S/N ratios. An equation to obtain this knock strength is expressed for example as follows, whereby the S/N ratio is obtained through adding operation.
[0045] When the knock strength is obtained in step 105 it is compared with a predetermined value obtained in step 106 for knock determination. When it is judged that the knock strength obtained in step 105 is larger than the predetermined value, the occurrence of a knocking is identified in step 107.
[0046] Then, a knock flag "1" indicative of the occurrence of a knocking is set in step 108. This knock flag is utilized in an ignition control task which is activated separately.
[0047] On the other hand, when the knock strength is judged to be smaller than the predetermined value at step 106, assuming that no knocking is taking place, it is judged in step 109 whether each background level BGLi is larger than a predetermined limit value, namely in this embodiment, lower limiter BGLMTi. Thereby, in this embodiment of the invention, BGL1 ...... BGL8 are compared with corresponding BGLMT1 ...... BGLMT8, respectively.
[0048] When a background level is judged in step 109 to be greater than the lower limiter BGLMTi, that is, to be a normal background level, the background level BGLi is updated in step 110.
[0049] An update value for this background level BGLi is obtained by filter processing of the power spectrum of a selected frequency. More specifically, it is obtained for each one of the selected frequencies by calculating the following equation,
[0050] In contrast, when the background level BGLi is judged in step 109 to be smaller than the lower limiter BGLMTi, that is, the background level BGLi decreases abnormally, the lower limiter BGLMTi is set instead thereof in step 111 to be utilized as a BGLi in the next step 104 to follow.
[0052] Through the hereabove processing the knock detection routine is accomplished, then the knock flag set in this routine is utilized in the ignition control task. In addition, although the lower limiter herein is also utilized as a threshold value for background level determination, they may be provided separately.
[0054] Various modifications of the lower limiter BGLMTi of the invention may be considered, but the most typical examples of which will be such methods: one is by storing data; the other is through calculation thereof. They will be described more specifically in the following.
[0055] With reference to Figure 10, a method for setting of a lower limiter BGLMTi according to mapping is shown, where it is set for respective engine speeds such as 1000 rpm, 2000 rpm, 3000 rpm in this embodiment, and corresponding to respective cylinders (from 1 to 6 cylinders in this example) and respective resonance frequencies (fo ······ fi).
[0056] By adopting such mapping according to the invention, it is possible to set a very high-precision BGLMTi.
[0057] Further, these three parameters of the engine speeds, cylinder numbers and frequencies cited hereabove are not limited thereto, and it should be construed that it is also possible to set an appropriate BGLMTi with at least one of these parameters. A preferred result has been obtained, however, when the BGLMTi is set at least for respective frequencies. As a matter of course, it is possible for any BGLMTi stored in the map in Figure 10 to be retrieved through step 113 in Figure 11 by referring to a corresponding engine speed, cylinder number, and frequency. The step 113 shown in Figure 11 is inserted for execution thereof between steps 106 and 109 in Figure 1.
[0058] On the other hand, with reference to Figures 12 and 13, the method for obtaining BGLMTi by calculation will be described in the following.
[0059] Figure 12 is a schematic diagram to help understand an underlying concept thereof. A maximum value and a minimum value are obtained for each frequency thereby to derive a mean value BGLmean. Then, this mean value BGLmean is divided into by n (n=integer) so as to provide a lower limiter BGLMTi.
[0060] How to obtain these mean value BGLmean and lower limiter BGLMTi are described more specifically in steps 114 and 115 in Figure 13, where in step 114 a maximum value of the background level BGLup and a minimum value of BGLBP are added and divided by 2 for each frequency, then summed up from 1 to m (for example, 16 times), then divided by m to obtain the BGLmean, next in step 115 thusly obtained BGLmean is divided by n thereby to obtain the lower limiter BGLMTi. As a matter of course, it is possible to obtain respective BGLMTi corresponding to respective cylinder numbers, engine driving conditions as well.
[0061] Steps 114 and 115 in Figure 13 are inserted for execution between step 106 and step 109 in Figure 1.
[0062] By way of example, regarding a constant 1/n used in obtaining the lower limiter BGLMTi from the mean value BGLmean, a 1/3 is found to be able to provide the best BGLMTi.
[0063] The knock signal indicative of the knock occurrence thus obtained is utilized in the ignition task which will be described in detail in the following.
[0064] Figure 14 shows a system configuration diagram of the ignition apparatus. Air is introduced through an intake port of an air cleaner 1, then passes through an air duct 3, a throttle body 5 having a throttle valve, and an air supply tube 6 to be admitted into the cylinders of an engine 7. An inlet air quantity is detected by a hot wire air flow sensor 2 mounted on the air duct 3, and a detected signal is input into a control unit 9.
[0065] On the other hand, fuel supplied from a fuel tank (not shown) is injected through an injector 16, mixed with intake air in the intake passage, then supplied into the cylinders of the engine 7. Air fuel mixture is compressed by the engine 7, ignited by an ignition plug 15, then after explosion the exhaust gas is exhausted from an exhaust pipe 8. An exhaust sensor 11 is mounted on the exhaust pipe 8, and a detected signal detected thereby is input into the control unit 9.
[0066] A high voltage generated by an ignition coil 13 is distributed to each cylinder by a distributor 14 to be supplied to each ignition plug 15. An engine speed is detected by a crank angle sensor 12. The crank angle sensor 12 outputs a reference signal Ref indicating an absolute position for every rotation thereof and a Pos signal indicating a position thereof which is shifted by a predetermined angle from said absolute position. The Ref signal and the Pos signal are input into the control unit 9 as well. A vibration sensor 151 is mounted on the engine 7 for detection of vibration thereof, and a detection signal therefrom is input into the control unit 9.
[0067] The control unit 9 in response to signals from respective sensors calculates an optimum fuel supply quantity, ignition timing and the like, then outputs a control signal thus calculated to the injector 16 and the ignition coil 13 respectively.
[0068] Figure 15 shows in detail a configuration diagram of the control unit 9 of the invention. The control unit 9 is divided into two blocks of a control block 34 and a knocking detecting block 35: the control block 34 comprising a CPU 20, an A/D converter 21, a ROM 22, an input I/O 23, a RAM 24, a DPRAM 25, an output I/O 26 and a bus 37; and the knocking detecting block 35 comprising a CPU 29, a port 27, a timing circuit 28, an A/D converter 30, a ROM 31, a RAM 32, a clock 33, an operational circuit 38 and a bus 36. By way of example, exchange of data between the CPU 20 and CPU 29 is executed through the DPRAM 25 which is a dual port RAM.
[0069] An intake air flow Qa detected by the hot wire air flow meter 2 is converted into a digital value through the A/D converter 21, then is input into the CPU 20. Further, a Ref signal and a Pos signal detected by the crank angle sensor 12 are input into the CPU 20 through the input I/O 23. The CPU 20 executes arithmetic operation of thus entered signals according to a program stored in the ROM 22, then the result of the arithmetic operation is output through the output I/O 26 as a fuel injection time interval signal Ti which designates a fuel injection amount, and an ignition timing signal θign to respective associated actuators. Data storage for storing data required in the arithmetic operation is implemented by the RAM 24.
[0070] On the other hand, when the operational circuit 35 generates a top dead center (TDC) signal, the timing circuit 28 in response to the contents of data input by the CPU 20 through the port 27 divides a frequency signal generated and supplied from the clock 33, then generates on the basis of thus divided frequency signal a sampling signal. Upon occurrence of the sampling signal, the A/D converter 30 converts an output signal from the vibration sensor 15 into a digital value.
[0071] Prior art vibration sensors for use in detecting the knocking generally initiate resonance in the vicinity of 13 KHz, however, in this embodiment of the invention, in order to obtain resonance frequency components up to 18 to 20 KHz, such vibration sensors that resonate above 18 KHz are utilized.
[0072] The CPU 29 stores the sampled digital value in the RAM 32 according to the program stored in the ROM 31 as well as executes a frequency analysis thereof on the basis of the data stored according to the flowchart shown in Fig.1, thereby enabling detection of the occurrence of knocking taking place therein. The result of knocking occurrence detection is transmitted to the CPU 20 through the DPRAM 25.
[0073] Next, with reference to a flowchart in Figure 16, an arithmetic operation for obtaining an ignition timing in the CPU 20 will be described in the following. This flowchart operation is activated at a predetermined time cycle, for example, at every 10 msec. In step 201, an engine speed N and an intake air quantity Q are read out from predetermined registers set in the RAM 24. In the next step 202, an intake air quantity per unit engine speed Q/N is calculated, then from this Q/N is obtained a fuel injection time width Ti, then a basic ignition timing θbase is obtained from a set of basic ignition timing map stored in the ROM 22 to supply fuel in accordance therewith. In step 203, it is judged whether a knocking has occurred or not according to the contents of the knock flag set in the flowchart of Figure 1. If a knocking has occurred, a predetermined retard angle quantity Δθret is subtracted from an ignition timing θadv in step 213. By this subtraction, the ignition timing is retarded. In step 214, the retarded ignition timing retarded as the result of the knocking occurrence is compared with a predetermined speed, for example, 50 (as indicated in step 205) to determine the base for a value to be recovered. Count data A is initialized, then the step advances to 208.
[0074] On the other hand, when there occurred no knocking in step 203, the count data A is incremented by 1. The count data A is used to determine whether it is a time for the retarded ignition timing θadv retarded due to the occurrence of knocking to be recovered by a leading angle quantity Δθadv. In step 205, it is judged whether the count data A equals a predetermined value 50. Since the flowchart of Fig.16 is activated every 10 msec, it is 0.5 sec after initialization of the counter data A when the count data A becomes equal to 50, thus it is recovered every 0.5 sec. When the count data A is not equal to 50 in step 205, the step advances to 206. In step 206, a predetermined leading angle quantity Δθadv is added to the retard angle value θadv. By this addition, the ignition timing is effectually recovered.
[0075] Next, in step 208, an ignition timing θign is calculated by adding the ignition timing θadv hereinabove obtained to the basic ignition timing θbase. In step 209, a maximum lead angle value θres is obtained corresponding to the engine speed N and the unit value Q/N of the intake air quantity to engine speed. Obtaining of the maximum lead angle value θres is executed by reading from the maximum lead angle value map stored in the ROM 31. In step 210 it is judged whether the ignition timing θign has exceeded the maximum lead angle value θres or not. If not, the step advances to 211. If exceeded the maximum lead angle value θres, the lead angle being too excessive, the maximum lead angle value θres is set as an ignition timing θign in step 211.
[0076] Finally, after setting of the ignition timing θign, a delay time td, a sampling number ns and a frequency division ratio ts corresponding to an engine state are output to the port 27 in step 212.
[0077] By way of example, according to the frequency division ratio ts, a sampling cycle for sampling output digital values from the vibration sensor is determined, and according to the sampling number ns the number of sampling is determined.
[0078] As hereinabove set forth, through detection of knocking from the plurality of resonance frequency components and by controlling the ignition timing appropriately responsive thereto, the occurrence of knocking in the engine can be eliminated.
[0079] For the hereinabove knock occurrence signals to be utilized in the ignition control task there is set basically for each frequency a lower limiter BGLMTi as shown in Figs. 1, 10, 12. However, if any particular resonance frequency band is known in advance in which the background level is anticipated to fall abnormally, it is possible to set a lower limiter corresponding to such frequency band alone. For example, with reference to Figure 6, if it is known in advance that background levels corresponding to resonance frequencies f1 and f2 will fall, only the lower limiters BGLMT1 and BGLMT9 alone may be set.
[0080] Further, in case a full range of lower limiters BGLMTi as in Figure 10 cannot be prepared because of the limits in terms of amounts of calculation involved and map capacity required, the following alternate method may be adopted.
[0081] That is, a limited number of representative lower limiters BGLMTs corresponding to typical resonance frequencies, representative cylinders or some typical engine driving conditions may be selected to be set for use in common.
[0082] First, Figure 17 illustrates setting of lower limiters BGLMTs with respect to a particular typical resonance frequency.
[0083] A map in Figure 17 is prepared corresponding both to respective cylinders and respective engine speeds with respect to a particular resonance frequency fi=6.3 KHz.
[0084] Thereby, a lower limiter BGLMT determined corresponding to a particular cylinder number and a particular engine speed is used in common for comparison with each background level BGLi corresponding to the selected resonance frequency.
[0085] That is, in step 116 shown in Figure 18, a corresponding lower limiter BGLMT is retrieved corresponding to a specific engine speed and a specific cylinder number from the map of Figure 17. Then, in step 117, a comparison is carried out for each resonance frequency BGLi with the common lower limiter BGLMT. These two steps are inserted between steps 106 and 109 in Figure 1. As a matter of course, step 117 is intended to replace step 109. Further, it should be construed that BGLMTi in step 111 is a common lower limiter BGLMT.
[0086] Figure 19 shows an example of a map prepared corresponding to respective frequencies and respective engine speeds with respect to a particular number of cylinders 3.
[0087] Thereby, a lower limiter BGLMT to be determined at a cross point corresponding to a respective frequency and a respective engine speed is used for comparison with each background level BGLi of the selected resonance frequency.
[0088] Namely, as shown in Figure 20, a corresponding lower limiter BGLMT corresponding to a specific engine speed and a specific frequency is retrieved from the map of Figure 19, then in step 119 a comparison of the corresponding lower limiter BGLMT with a background level is carried out for respective resonance frequency. Thereby, since it is used in common as the lower limiter for each cylinder, these steps are inserted between steps 106 and 109 in Figure 1. Step 119 is intended to replace step 109.
[0089] Figure 21 shows an example of a map formulated corresponding to respective resonance frequencies and respective cylinders, intended for use in a specific driving condition of the engine. That is, the specific engine speed selected herewith is used as a parameter in common.
[0090] Thereby, a lower limiter BGLMT to be determined at a position in coincidence corresponding to a particular frequency and a particular cylinder number is used in common for comparison with a respective background level BGLi of the selected resonance frequency.
[0091] Namely, in step 120 in Figure 22, a corresponding lower limiter BGLMT corresponding to a specific frequency and a specific cylinder number is retrieved from the map of Figure 21, then in step 121 this corresponding lower limiter BGLMT is used for comparison with a background level for respective resonance frequencies. Thereby, since it is used in common as the lower limiter for the selected engine speed, these steps are inserted between steps 106 and 109 in Figure 1. It should be construed, however, that the step 121 replaces the step 109.
[0092] When it is required further to reduce the calculation loads and mapping memory capacities, it is also possible to set up the best mode of a lower limiter BGLMT obtainable in the most desirable conditions with respect to the resonance frequencies, cylinder numbers and engine speeds, respectively.
[0093] That is, only one lower limiter BGLMT is effected to be set irrespective of respective resonance frequencies, cylinder numbers and engine speeds. Thereby, this only one lower limiter is stored alone in a ROM area.
[0094] With reference to Figure 23, another embodiment of the invention will be set out in the following. Since the basic configuration thereof is the same as in Figure 1, only the gist thereof will be described.
[0095] In Figure 23, step 122 is executed when it is judged in step 106 that no knocking has occurred, and in step 122 the singular lower limiter BGLMT thus set hereinabove irrespective of respective resonance frequencies, cylinder numbers, engine speeds is effected to be compared with a background level BGLi corresponding to each resonance frequency. When it is judged as a result of the comparison that any background level BGLi is smaller than the lower limiter BGLMT, the lower limiter BGLMT is set up in step 123 instead thereof so as to ensure that in the next recurring step 104 the BGLi is replaced by the BGLMT and each S/N ratio is obtained thereby for each frequency.
[0096] Further, the concepts and methods of the invention described in Figures 17 through 23 may be implemented by calculations as well, according to the calculational method as specified in Figure 13.
[0097] Still further, a method for obtaining the background level BGLi in the various embodiments of the invention described heretofore is based on the following equation for applying a filter processing to a signal intensity fi,
However, it may be obtained by the usual integral method of integrating background level measurement as well.
[0098] Further, although the power spectrum SLi is obtained from the S/N ratio, it may be obtained as well from a difference from the background level BGLi, i.e., SLi=fi-BGLi. Thereby, a knock strength S may be obtained by adding up this difference.
[0099] Still further, although it is judged that there occurred knocking when an added value of the power spectra of the plurality of frequencies exceeds a preset value, there may be provided a logic which prescribes the occurrence of a knocking if any one of the power spectra of the plurality of frequencies exceeds a preset value, without going through addition of respective power spectra.
[0100] In the next, there will be described a compensation method for compensating for a side effect occurring when the background level BGLi is obtained through the filter processing thereof.
[0101] Since the background level BGLi in the one embodiment of the invention shown in Figure 1 is obtained through the delay filter processing, there arises a problem in a transient state of the engine such as acceleration or the like that the background level BGLi cannot follow up the transient state and thereby that an apparent S/N increases.
[0102] The lower limiter BGLMTi according to the present invention is effective also to deal with such follow-up delays of BGLi as well, but it is further advantageous to change the lower limiter BGLMTi according to acceleration and steady state operation.
[0103] Figure 24 shows transient-state and steady-state lower limiters BGLMTi, where the transient-state limiter is set at a larger value.
[0104] Figure 25 shows changes, in a transient state, of the throttle valve opening, engine speeds, background level BGLi and lower limiter BGLMTi, wherein it is judged according to a degree of the throttle valve opening per unit period of time whether is a rapid acceleration or a slow acceleration, and depending on either it is a rapid acceleration or a slow acceleration a magnitude of the lower limiter BGLMTi is adjusted. This adjustment is effected either by multiplying the lower limiter BGLMTi for use in the steady-state operation by a constant or adding thereof.
[0105] The foregoing flowchart will be described with reference to Figure 26, where in step 124 a degree of throttle opening is determined in what level it is; if it is a rapid acceleration, intermediate acceleration, slow acceleration or any other driving condition. Then, when it is judged to be a rapid acceleration in step 125, the steady-state lower limiter BGLMTi is multiplied by a coefficient 1.5, when it is judged to be an intermediate acceleration in step 126 the steady-state lower limiter BGLMTi is multiplied by a coefficient 1.3, when it is judged to be a slow acceleration in step 127 the steady-state lower limiter BGLMTi is multiplied by a coefficient 1.1, and when it is judged to be a steady coursing, the lower limiter BGLMTi is set as it is in step 128. These steps are inserted for execution between steps 106 and 109 in Fig.1.
[0106] Through such arrangement, an appropriate lower limiter BGLMTi can be obtained for various driving conditions of the engine.
[0107] In the embodiments of the invention described heretofore, attention has been directed to such cases where the background level abnormally drops. However, there may also take place such a phenomenon where the background level abnormally rises.
[0108] In such a case as above, an effective countermeasure can be provided by setting up an upper limiter instead of the lower limiter likewise in step 109 in the foregoing embodiment of the invention, .
[0109] In this case also, it should be construed that the upper limiter can take a variety of modifications of value likewise the case of the lower limiter.
[0110] Further, it will be more advantageous to provide for a countermeasure against such inconveniences anticipated to take place as will be described in the following.
[0111] Namely, gain of the background level indicating an amplification degree thereof is switched, for example, to 1/2 at a predetermined timing by means of hardware, and in line with this switching the power spectrum of each frequency is switched to 1/2 by means of software.
[0112] However, when the power spectrum of each frequency happens to drop abnormally, although the background gain is ensured to be switched by the hardware, there occurs sometimes a problem that the power spectrum of each frequency fails in switching due to an error in quantization, consequently increasing the S/N ratio abnormally, thereby causing an erroneous knocking detection.
[0113] In order to solve such problems, the following steps are added between steps 103 and 105 in Figure 27 according to the invention.
[0114] First, in step 129 following step 103 it is judged for each frequency fi whether its strength is larger than/ equal to a preset lower limiter fLMTi, or not. If it is judged here to be larger/equal thereto, the step advances to 104 where to execute an ordinal S/N ratio calculation.
[0115] On the other hand, in step 129 following step 103 if it is judged for each frequency fi that its strength is smaller than a preset lower limiter fLMTi, the step advances to 130 where an S/N ratio of the frequency spectrum fi to the background level is set at "1". That is, there is executed a processing thereby for assuming that no knocking is present with respect to the corresponding frequency.
[0116] Next in step 131, the corresponding frequency spectrum is replaced by the predetermined lower limiter fLMTi, then the step advances to 105 where a knock strength calculation is executed.
[0117] As hereinabove stated, the problem associated with the prior art that S/N ratio increases abnormally due to the quantization error taking place when the intensity of each frequency drops abnormally can be solved by setting a lower limiter instead of that erroneous frequency intensity.
[0118] Also in this preferred embodiment of the invention, it should be construed that the value of a lower limiter corresponding to each frequency may take a variety of modified value likewise the foregoing embodiment of the background lower limiter.
[0119] The merits and advantageous effects according to the present invention will be summarized as follows. Even if the background level is varied abnormally, because of the arrangement of the invention, the abnormally changing background level is altered to a predetermined limit value, thereby ensuring effective information indicative of a knocking occurrence to be obtained.
[0120] Thereby, such problems can be solved that take place when notwithstanding that the plurality of resonance frequencies are sampled for detection of the occurrence of any knocking, if there happens an error signal indicating the occurrence of a false knocking in at least one of the frequency bands, the error signal adversely affects the general judgement on the knocking based on the resonance frequencies in general, thereby in consequence remarkably improving reliability of knock detection apparatus.
extracting a plurality of characteristic components (fi) indicative of knocking from physical quantities (BGLi) relating to a knocking state in the internal combustion engine, and a comparison component to be defined according to said physical quantities;
extracting information on knocking (107, 108, 112) from a relationship (106) between said plurality of characteristic components and said comparison component; and
setting a limit value (fLMTi, BGLMTi) to either one of said plurality of characteristic components and said comparison component.
a predetermined limit comparison component is substituted for at least one of said plurality of comparison components when the value of which is outside an allowable extent.
a predetermined limit comparison component is substituted to be utilised in common for any comparison component which is judged outside the limit of the allowable value.
executing a frequency analysis of a vibration representing a knocking state of an internal combustion engine and the step of
extracting information on knocking is derived from a relationship between a plurality of characteristic frequency components indicative of the knocking which are selected from the frequencies subjected to said frequency analysis and a comparison component which is obtained by applying a predetermined filtering processing to said characteristic frequency component and said restricting step includes
substituting a limit comparison component for said comparison component when said comparison component becomes smaller than said limit comparison component.
said comparison component is set respectively corresponding to said plurality of characteristic frequency components; and
said limit comparison component is also set respectively corresponding to said plurality of characteristic frequency components.
it is judged whether any one of said plurality of characteristic components is outside a permissible extent of value or not; and
a predetermined limit characteristic component is substituted for said any one of plurality of characteristic components when the same is judged to be outside said permissible extent of value thereof.
it is judged whether all of said plurality of characteristic components is within a permissible extent of value corresponding thereto or not; and
a predetermined limit characteristic component is substituted for any one of the characteristic components which is outside the permissible extent of value.
it is judged whether all of said plurality of characteristic components is within one permissible limit of value or not; and
a predetermined limit characteristic component is substituted for any one of the characteristic components which is outside said one permissible limit of value.
substituting said respective limit characteristic component corresponding thereto for any one of a plurality of characteristic components which is judged to be smaller than said respective limit characteristic component.
extracting a plurality of characteristic components (fi) indicative of a knocking from physical quantities (BGLi) relating to a knocking state in an internal combustion engine, and a plurality of comparison components to be defined according to said physical quantities;
extracting information on the occurrence of knocking (107, 108, 112) from a relationship (106) between said plurality of characteristic components and said plurality of comparison components;
adjusting an ignition timing in such a manner as to suppress a knocking upon occurrence thereof;
updating one of said comparison components, when there exists no knocking, with a new value which is within a range of values permitted for said comparison component to take; and
updating one of said comparison components with a predetermined limit comparison component when said comparison component is outside the permissible extent of values thereof.
judging the occurrence of knocking when a sum of at least two of said components ratios becomes greater than a predetermined value;
adjusting the ignition timing in such a manner as to suppress the knocking upon the occurrence thereof as judged to have occurred as above;
determining, upon judgment that there exists no knocking when the sum of said at least two component ratios is smaller than said predetermined value, whether said respective comparison components are greater than respective limit comparison components corresponding thereto otherwise than one limit comparison component particularly selected;
updating said respective comparison components with respective new values when they are greater than the limit comparison component; and
updating said respective comparison components with respective limit comparison components corresponding thereto or with said one limit comparison component when said respective comparison components are smaller than the limit comparison component(s).
Extrahieren einer Mehrzahl charakteristischer Komponenten (fi), die einen Klopfzustand anzeigen, aus physikalischen Größen (BGLi), die sich auf einen Klopfzustand in der Brennkraftmaschine beziehen, sowie einer Vergleichskomponente, die gemäß der genannten physikalischen Größen definiert wird;
Extrahieren von Daten über einen Klopfzustand (107, 108, 112) aus einem Verhältnis (106) zwischen der genannten Mehrzahl charakteristischer Komponenten und der genannten Vergleichskomponente; und
Festlegen eines Grenzwertes (fLMTi, BGLMTi) bezüglich der genannten Mehrzahl von charakteristischen Komponenten und der genannten Vergleichskomponente.
wobei mindestens eine Vergleichskomponente aus der Mehrzahl von Vergleichskomponenten durch eine vorbestimmte Grenzwert-Vergleichskomponente ersetzt wird, wenn der Wert der entsprechenden Komponente außerhalb eines zulässigen Bereichs liegt.
eine Grenzwert-Vergleichskomponente gemeinsam für alle Komponenten der Mehrzahl von Vergleichskomponenten eingesetzt wird, die sich außerhalb des Bereichs zulässiger Werte befinden.
Ausführen einer Frequenzanalyse einer Schwingung, die einen Klopfzustand einer Brennkraftmaschine darstellt und den Schritt des
Extrahierens von Daten über den Klopfzustand aus dem Verhältnis zwischen einer Mehrzahl charakteristischer Frequenzkomponenten, die einen Klopfzustand anzeigen, die aus den Frequenzen der Frequenzanalyse ausgewählt werden, und einer Vergleichskomponente, die durch die Ausführung eines vorbestimmten Filterverfahrens an der charakteristischen Frequenzkomponente gewonnen wird, und wobei der genannte Begrenzungs- bzw. Einschränkungsschritt folgendes umfaßt:
Ersetzen der genannten Vergleichskomponente durch eine Grenzwert-Vergleichskomponente, wenn die genannte Vergleichskomponente kleiner ist als die genannte Grenzwert-Vergleichskomponente.
die genannte Vergleichskomponente entsprechend im Verhältnis zu der genannten Mehrzahl charakteristischer Frequenzkomponenten festgelegt wird; und wobei
die genannte Grenzwert-Vergleichskomponente ebenfalls entsprechend im Verhältnis zu der genannten Mehrzahl charakteristischer Frequenzkomponenten festgelegt wird.
wobei festgestellt wird, ob sich eine der Komponenten der genannten Mehrzahl charakteristischer Komponenten außerhalb des genannten zulässigen Wertebereichs der Komponenten befindet oder nicht; und wobei
eine vorbestimmte charakteristische Grenzwert-Komponente eine Komponente aus der Mehrzahl charakteristischer Komponenten ersetzt, wenn in bezug auf diese Komponente festgestellt wird, daß sie sich außerhalb des zulässigen Wertebereichs für die Komponenten befindet.
wobei festgestellt wird, ob sich alle Komponenten der genannten Mehrzahl charakteristischer Komponenten innerhalb des genannten zulässigen Wertebereichs der Komponenten befinden oder nicht; und wobei
eine vorbestimmte charakteristische Grenzwert-Komponente eine Komponente aus der Mehrzahl charakteristischer Komponenten ersetzt, die sich außerhalb des zulässigen Wertebereichs für die Komponenten befindet.
wobei festgestellt wird, ob sich alle Komponenten der genannten Mehrzahl charakteristischer Komponenten innerhalb des genannten zulässigen Grenzwertes befinden oder nicht; und wobei
eine vorbestimmte charakteristische Grenzwert-Komponente eine Komponente aus der Mehrzahl charakteristischer Komponenten ersetzt, die sich außerhalb des zulässigen Grenzwertes befindet.
eine entsprechende charakteristische Grenzwert-Komponente eine charakteristische Komponente ersetzt, für die festgestellt worden ist, daß sie kleiner ist als die genannte entsprechende charakteristische Grenzwert-Komponente.
Extrahieren einer Mehrzahl charakteristischer Komponenten (fi), die einen Klopfzustand anzeigen, aus physikalischen Größen (BGLi), die sich auf einen Klopfzustand in der Brennkraftmaschine beziehen, sowie einer Mehrzahl von Vergleichskomponenten, die gemäß der genannten physikalischen Größen definiert werden;
Extrahieren von Daten über das Auftreten eines Klopfzustandes (107, 108, 112) aus einem Verhältnis (106) zwischen der genannten Mehrzahl charakteristischer Komponenten und der genannten Mehrzahl von Vergleichskomponenten;
Einstellen der Zündzeitpunktverstellung, so daß ein Klopfen bei dessen Auftreten unterdrückt wird;
Aktualisieren einer der genannten Vergleichskomponenten wenn kein Klopfen vorliegt durch einen neuen Wert, der sich innerhalb eines Wertebereichs befindet, der für die genannte Vergleichskomponente zulässig ist; und
Aktualisieren einer der genannten Vergleichskomponenten mit einer vorbestimmten Grenzwert-Vergleichskomponente, wenn sich die genannte Vergleichskomponente außerhalb des zulässigen Wertebereichs für die Komponenten befindet.
Feststellen des Auftretens eines Klopfzustandes, wenn eine Summe von mindestens zwei der genannten Komponenten größer ist als ein vorbestimmter Wert;
Einstellen der Zündzeitpunktverstellung, so daß ein Klopfen bei dessen Auftreten unterdrückt wird, und zwar gemäß der Feststellung des obengenannten Auftretens des Klopfens;
Bestimmen, nach der Feststellung, daß kein Klopfen existiert, wenn die Summe von mindestens zwei Komponentenverhältnissen kleiner ist als der genannte vorbestimmte Wert, ob die genannten entsprechenden Vergleichskomponenten größer sind als entsprechende Grenzwert-Vergleichskomponenten, oder ansonsten als eine bestimmte ausgewählte Grenzwert-Vergleichskomponente;
Aktualisieren der entsprechenden Vergleichskomponenten mit entsprechenden neuen Werten, wenn diese größer sind als die Grenzwert-Vergleichskomponente; und
Aktualisieren der genannten entsprechenden Vergleichskomponenten mit entsprechenden Grenzwert-Vergleichskomponenten, die diesen entsprechen, oder mit der genannten einen Grenzwert-Vergleichskomponente, wenn die entsprechenden Vergleichskomponenten kleiner sind als die Grenzwert-Vergleichskomponente(n).
extraire une pluralité de composantes caractéristiques (fi) indicatives d'un cognement à partir de quantités physiques (BGLi) associées à un état de cognement dans le moteur à combustion interne, et une composante de comparaison devant être définie en fonction desdites quantités physiques ;
extraire une information relative au cognement (107, 108, 112) à partir d'une relation (106) entre ladite pluralité de composantes caractéristiques et ladite composante de comparaison ; et
régler une valeur limite (fLMTi, BGLMTi) sur l'une de ladite pluralité de composantes caractéristiques et de ladite composante de comparaison.
une composante de comparaison limite prédéterminée est substituée à au moins l'une de la pluralité de composantes de comparaison lorsque la valeur de cette composante est à l'extérieur d'une gamme admissible.
une composante de comparaison limite prédéterminée est substituée pour être utilisée en commun pour n'importe quelle composante de comparaison qui est évaluée comme étant en dehors de la limite de la valeur admissible.
exécuter une analyse de fréquences d'une vibration représentant un état de cognement d'un moteur à combustion interne, et l'étape consistant à
extraire une information sur le cognement, qui est dérivée d'une relation entre une pluralité de composantes de fréquences caractéristiques indicatives du cognement, qui sont sélectionnées à partir des fréquences soumises à ladite analyse de fréquences, et une composante de comparaison, qui est obtenue par application d'un procédé de filtrage prédéterminé à ladite composante de fréquence caractéristique, et ladite étape de limitation consiste à
substituer une composante de comparaison limite à ladite composante de comparaison lorsque ladite composante de comparaison devient inférieure à ladite composante de comparaison limite.
ladite composante de comparaison est réglée de manière à correspondre respectivement à ladite pluralité de composantes de fréquences caractéristiques ; et
ladite composante de comparaison limite est également réglée de manière à correspondre respectivement à ladite pluralité de composantes de fréquences caractéristiques.
une évaluation est faite pour savoir si l'une quelconque de ladite pluralité de composantes caractéristiques se situe ou non à l'extérieur d'une gamme admissible de valeurs ; et
une composante caractéristique limite prédéterminée est substituée à ladite composante parmi la pluralité de composantes caractéristiques lorsque cette composante est évaluée comme étant située à l'extérieur de ladite gamme admissible de valeurs de cette caractéristique.
une évaluation est faite pour savoir si l'ensemble de ladite pluralité de composantes caractéristiques se situe ou non dans une gamme admissible de la valeur correspondant à ces composantes ; et
une composante caractéristique limite prédéterminée est substituée à l'une quelconque des composantes caractéristiques qui est située à l'intérieur de la gamme admissible de valeurs.
une évaluation est faite pour déterminer si l'ensemble de ladite pluralité de composantes caractéristiques est inférieure ou non à une limite admissible de valeur ; et
une composante caractéristique limite prédéterminée est substituée à l'une quelconque des composantes caractéristiques qui se situe à l'extérieur de ladite limite admissible de valeur.
on substitue ladite composante caractéristique limite respective, qui lui correspond, à l'une quelconque d'une pluralité de composantes caractéristiques, qui est évaluée comme étant inférieure à ladite composante caractéristique limite respective.
extraire une pluralité de composantes caractéristiques (fi) indicatives d'un cognement à partir de quantités physiques (BGLi) concernant un état de cognement dans un moteur à combustion interne, et une pluralité de composantes de comparaison devant être définies conformément auxdites quantités physiques ;
extraire une information concernant l'apparition de cognement (107, 108, 112) à partir d'une relation (106) entre ladite pluralité de composantes caractéristiques et ladite pluralité de composantes de comparaison ;
régler une séquence d'allumage de manière à réduire un cognement lors de l'apparition de ce dernier ;
mettre à jour l'une desdites composantes de comparaison lorsqu'il n'existe aucun cognement, avec une nouvelle valeur qui est située dans une gamme de valeurs que l'on peut prendre pour ladite composante de comparai-son ; et
mettre à jour l'une desdites composantes de comparaison avec une composante de comparaison limite prédéterminée lorsque ladite composante de comparaison est située de dehors de la gamme admissible de valeurs de cette composante.
évaluer l'apparition d'un cognement lorsqu'une somme d'au moins deux desdits rapports de composantes devient supérieure à une valeur prédéterminée ;
régler la séquence d'allumage de manière à réduire le cognement lors de son apparition lorsqu'il est évalué comme étant apparu comme indiqué précédemment ;
déterminer, lors de l'évaluation du fait qu'il n'existe aucun cognement lorsque la somme desdits au moins deux rapports de composantes est inférieure à ladite valeur prédéterminée, si lesdites composantes de comparaison respectives sont supérieures à des composantes de comparaison limites respectives qui leur correspondent, ou sinon à une composante de comparaison limite sélectionnée de façon particulière ;
mettre à jour lesdites composantes de comparaison respectives avec de nouvelles valeurs respectives lorsqu'elles sont supérieures à la composante de comparaison limite ; et
mettre à jour lesdites composantes de comparaison respectives avec lesdites composantes respectives de comparaison limites qui leur correspondent ou avec ladite composante de comparaison limite lorsque lesdites composantes de comparaison respectives sont inférieures à la ou aux composantes de comparaison limites.